Prior art has attempted to solve the problem of overturning of vehicles, such as tractors, or trucks, by either moving the center of gravity to a position in front of the rear axle increasing the maximum angle of attack or adding a lateral arm to the rear. Vehicles having booms for lifting weight have similar problems of stability when an overhanging load is present. The approach taken by prior art has been to add a stabilizing arm that is extended outward from the vehicle in a rigid manner changing the center of gravity of the entire vehicle relative to the overhanging load.
Cutler in U.S. Pat. No. 3,876,226 issued Apr. 8, 1975 teaches such an attachment of transverse arms to a vehicle. The specification discloses a subassembly for attaching an extending arm to a mower, or the like, having at least one axle carrying road wheels. The assembly is mounted to the chassis and/or body and transfers at least part of the vertical loads indirectly to the axle by the springs and subsequently transferring the overturning moment produced by the arm directly to the axle. The object of this invention is to provide mounting means for a lateral arm that automatically maintains the vehicles relative level despite the widely varying overturning moments applied due to the different working positions of the arm and the intermittent support given by the ground.
Torras in U.S. Pat. No. 4,515,392 issued on May 7, 1985 discloses a device for a tractor or similar vehicle intended for operation along sloping paths, such as hills, embankments, etc., particularly tractors used for mowing highway right-of-way areas. These tractors have sufficient power to traverse slopes beyond the angle of attack and are protected from overturning by the addition of a rigid tail plate mounted behind the rear axle of the vehicle contacting the travel path, limiting the maximum amount of tipping so that the front end of the vehicle can rise no more than a limited amount.